The present invention relates to an IC wiring connecting method for connecting the internal wirings of a semiconductor integrated circuit (hereinafter abbreviated to "IC") for debugging, correcting and analyzing faults, and an apparatus for carrying out the IC wiring connecting method.
The significance of finding incorrect design and faulty processes by cutting or connecting part of the internal wirings of a large-scale integrated circuit chip (hereinafter, abbreviated to "LSI chip") for debugging and correcting faults in the stage of development and improving the yield of the IC chip production line by reflecting the results of fault analysis on the process conditions has increased with the progressive increase in the density of integration and miniaturization of ICs. Several technical means utilizing a laser beam or an ion beam for such purposes have been proposed.
A first prior art is disclosed in "Laser Strip Cutting System for IC Debugging", Tech. Digest of CLEO'80, (1981) p.160. According to the first prior art, conductive lines are cut with a laser beam for debugging.
A second prior art is disclosed in Japanese Patent application No. 58-42126 (U.S. Pat. No. 4,699,899). The second prior art used an ion beam emitted from a liquid metal ion source and focused in a spot of 0.5 micronsorless in diameter for cutting the conductive lines, perforating and connecting the upper and lower conductive lines through deposition using the ion beam.
A third prior art is disclosed in "Direct Writing of Highly Conductive Mo Lines by Laser Induced CVD", Extended Abstract of 17th Conf. on Solid State Devices and Material, (1985) p. 193.
The first prior art relates only to means for cutting the wirings and to nothing about means for connecting the conductive lines.
The laser material processing method has disadvantages that (1) the heat generated by laser material processing is transferred by conduction to a portion surrounding a part being processed causing the evaporation and eruption of the materials, and hence it is very difficult to apply the laser material processing method to processing a minute part of 0.5 microns or less in-size, and (2) application of the laser material processing method to processing a thick insulating film of 2 microns or greater in thickness is difficult, because the laser beam is hard to be absorbed by the insulating film formed of SiO.sub.2 or Si.sub.3 N.sub.4 and is absorbed by the wiring formed of aluminum or polycrystalline silicon under the insulating film causing the evaporation and eruption of the materials forming the wiring, which explosively blows off the insulating film covering the wiring, and laser material processing damages seriously a portion surrounding the part being processed causing faults. Accordingly, it is difficult to apply the laser material processing method to processing the wirings of multilayer interconnection and highly integrated minute wirings.
The second prior art relates to (1) means employing a focused ion beam for cutting and perforating, and (2) means employing a focused ion beam for connecting multilayer wirings. The focused ion beam material processing is capable of processing a material of 0.5 microns or less in size, and is capable of processing layers sequentially from the upper layer by sputtering regardless of type of the material. Thus, the second prior art eliminates the disadvantages of the first prior art. However, the second prior art relates only to a procedure for connecting wirings formed in layers one over the other and not to means for connecting wirings arranged at different places, respectively.
According to the third prior art, a silicon substrate coated with a SiO.sub.2 film is irradiated by an ultraviolet laser beam in a gaseous ambient of an inorganic metal compound such as Mo(CO).sub.6 (molybdenum carbonyl) to deposit a metal such as molybdenum over the substrate through a photothermal or photochemical laser-induced CVD process for directly forming a metallic wiring pattern. However, the third prior art relates only to merely forming a wiring pattern of molybdenum over an insulating film, and to nothing about means for interconnecting wirings formed under insulating films, such as a protective film and insulating films formed between the layers of the wirings, which is an ordinary configuration of a practical IC.